haskell - Cabal 安装在构建 Yesod 项目时抛出 ExitFailure 1

Question

我是 Haskell Web 开发和框架的新手，我一直在关注 this tutorial 。我已经运行 yesod init 来创建一个项目。然后我进入项目文件夹并运行:

$ cabal sandbox init
$ cabal install --enable-tests --reorder-goals --max-backjumps=-1 -j

我到处遇到了一些依赖问题，但到目前为止已经解决了所有这些问题。现在我在构建过程中遇到了一个错误，我似乎找不到任何答案或修复。构建过程突然结束并出现 ExitFailure 1。

以下是完整的错误消息:

Model.hs:13:1:
Illegal instance declaration for
  ‘ToBackendKey
     persistent-2.0.8:Database.Persist.Sql.Types.SqlBackend Email’
  (All instance types must be of the form (T t1 ... tn)
   where T is not a synonym.
   Use TypeSynonymInstances if you want to disable this.)
In the instance declaration for
  ‘ToBackendKey persistent-2.0.8:Database.Persist.Sql.Types.SqlBackend Email’

Model.hs:13:1:
Illegal instance declaration for
  ‘ToBackendKey
     persistent-2.0.8:Database.Persist.Sql.Types.SqlBackend User’
  (All instance types must be of the form (T t1 ... tn)
   where T is not a synonym.
   Use TypeSynonymInstances if you want to disable this.)
In the instance declaration for
  ‘ToBackendKey persistent-2.0.8:Database.Persist.Sql.Types.SqlBackend User’
cabal: Error: some packages failed to install:
Wordscape-0.0.0 failed during the building phase. The exception was:
ExitFailure 1

还有其他人遇到过这样的错误/知道如何补救吗？任何帮助，将不胜感激。谢谢!

Answer 1

添加

{-# LANGUAGE TypeSynonymInstances #-}

Model.hs 顶部应该修复它，也应该升级到 persist-2.1(尽管您可能要到明天才能做到这一点)。